Jet blast cooling and quieting device



19, 1954 H. w. BURDETT, JR., ETAL 2,692,024

JET BLAST COOLING AND QUIETING DEVICE iled Nov. 25, 1950 3 Shets-Sheet l INVENTORS HARRY W. BURDETT, JR.

BERNARD PEARLMAN EDWARD A.NEU,JR.

AGENT Oct. 19, 1954 H. w. BURDETT, JR., ETAL 2,692,024

JET BLAST COOLING AND QUIETING DEVICE iled Nov. 25, 1950 3 Sheets-Sheet 2 JET BLAST lea.

FIG. 4

INVENTORS HARRY W. BURDETT,JR.

BERNARD PEARLMAN 5 EDWARD A.NEU,JR.

AGENT 19, 1954 H. w. BURDETT, JR., ETAL 2,692,024

JET BLAST COOLING AND QUIETING DEVICE 'iled Nov. 25, 1950 3 Sheets-Sheet 3 INITIAL MEAN TEMPERATURE /AND VELOCITY 0 JET TEMPERATURE m AND VELOCiTY Q [L /TEMPERATURE AND o VELOCITY REDUCTION 2000 l 4000 rc 3 *1 2 U FIN! L MEAN TEMPERATURE 3 AND VELOCITY m I000 5 I l 2000 r- COOLANT TEMPERATURE AND VELOCITY I O O O l 2 3 4 5 NOZZLE COOLANT DISTANCE AFT OF NOZZLE EXIT-FT.

EXIT INJECTION JET BLAST 7 INVENTORS HARRY W. BURDETT, JR.

BERNARD PEARLMAN EDWARD A.NEU,JR.

AGENT Patented Oct. 19, 1954 JET BLAST COOLING AND QUIE'JIIN G DEVICE Harry W. Burdett, Jr., Ridgewood, Bernard Pearlman, Morristown, and Edward A. Neu, Jr., Rockaway, N. J assignors to Reaction Motors, Inc., Bockaway, N. .l., a corporation of New Jersey Application November 25, 1950, Serial N 0. 197,622

3 Claims.

The present invention relates to apparatus for reducing the sound of and for cooling high velocity jets of hot gases. It relates more particularly to such a device for cooling, and quieting the sound of, the blast of hot gases of combustion from a reaction motor, especially those which burn a liquid fuel or fuels in a combustion chamber and expel the combustion products as a high velocity jet blast to create a propulsive thrust.

The present invention is particularly useful when it is applied to the jet blast from such a motor during static tests conducted in a populated location and on a test stand where the structure of the stand might be damaged by the heat and eroding effect of the blast.

It is well known that a high velocity jet of gas exhausted into the atmosphere will create a disturbance in the atmosphere and will cause a loud sound by the creation of compressional waves in the air. Where the high velocity ejection of gases is brought about by the combustion of fuel in a reaction motor the sounds of combustion are added to the other sound, thus producing a very loud and unpleasant noise, particularly where the reaction motor is of the rocket type wherein the gases are ejected at an extremely high velocity. Furthermore, the combustion within the reaction motor has heated these gases to a very high temperature in order that the high ejection velocity will be attained. Thus, the jet blast is at a very high temperature as well as at very high velocity thereby presenting the two-fold problem of temperature reduction as well as sound reduction.

It is, therefore, an object of the present invention to provide apparatus independent of the motor, which will effectively lower the temperature of the jet of hot gases emanating from a reaction motor without reducing the efficiency of the motor.

It is another object of the present invention to provide apparatus independent of the motor which will reduce the sound created by the high velocity jet of exhaust gases issuing into the atmosphere from a reaction motor without reducing the efficiency of the motor.

It is a principal object of the present invention to provide a single device wherein the foregoing objects of cooling and reducing the sound of jets of hot, high velocity gases are realized.

Other objects and advantages of the present invention will become apparent from the general and detailed description which follows.

In the drawings:

Figure 1 is a front view of a coolant frame utilizing transverse parallel outlet conduits.

Figure 2 is a side view of the coolant frame showing the manner in which it is used in the jet blast of a reaction motor.

Figure 3 is a front view of a coolant frame utilizing transverse open ended parallel conduits.

Figure 4 is a perspective view of one of the coolant emission conduits.

Figure 5 is a perspective view of one of the coolant emission conduits showing an elongated emission opening facing diagonally downstream of the jet blast.

Figure 6 is an illustrative curve chart showing estimated values of the jet blast and velocity drop.

Figure 7 is a front view of a coolant frame utilizing a circular header and radial open-ended outlet conduits.

Due to the high velocity and temperature of the hot gases emanating from reaction motors, particularly those of the rocket type, the unconfined jet blast remains dangerously hot for a considerable distance behind the exhaust outlet of the motor. Since it is often desirable to test such motors in a vertical or near vertical position, simulating a rocket vehicle takeoff attitude, it becomes important to cool the blast in order to protect the testing equipment and the structure of the test stand from damage due to the high temperature and extreme velocity.

In general, the present invention comprises a frame or rack of pipes through the interior of which a fluid coolant can be made to flow, this frame of pipes or conduits being placed in the path of flow of the unconfined jet blast as shown in Figure 2 and so arranged that a coolant fluid, such as water, can be pumped through the pipes and discharged within the confines of the jet blast. The addition of coolant to the jet blast absorbs energy from the jet and thus reduces the mean velocity and temperature of the jet as this energy is expended 'in heating and accelerating of the coolant to a new jet mean velocity and temperature. This is graphically indicated in Figure 6 which is an illustrative curve chart based on purely estimated values from visual and auditory observations made during actual tests with rocket motors. It will be seen in the figure that the temperature and velocity of the jet blast at the nozzle exit are very high, ordinarily of the order of about 3000 degrees Fahrenheit and about 6000 feet per second as shown. The introduction of coolant at a normal temperature of about '70 degrees Fahrenheit and at a distance of one foot from the nozzle exit can be expected to result in a substantial and rapid drop in temperature and velocity to levels estimated as 1200 degrees Fahrenheit and 2200 feet per second at a distance of about four feet from the nozzle exit. At a temperature such as this, test stand structure and equipment in the vicinity is much less likely to be damaged, and at the lower velocity the sound of the jet blast will be considerably reduced. Another factor also enters into the reduction in velocity with consequent further reduction in sound. This is the placement of the coolant emission frame close to the exhaust outlet of the reaction motor thus shortening the free length of the jet blast stream, resulting in an early diffraction of the pattern of compressional sound waves existent in the high velocity jet by the physical resistance of the frame in the path of the blast.

. One type of coolant delivery and emission frame is shown in Figure 1. It comprises a series of pipes or conduits l0, l2, [-3, I6 and I! connected into a U-shaped arrangement by means of T connection II and elbows I4 and I5 in the manner shown, the upper ends of pipes l6 and I! being closed by pipe caps 20 and 2|. Across the opening of this U-shaped frame are a number of pipes or conduits I 8 of smaller diameter than headers l6 and I1, each having a series of holes or orifices IS in its exterior facing substantially downstream of the jet blast. Orifices 19 are faced downstream in order to aid the flow of coolant by taking advantage of the aspirating effect created by the high velocity flow of gases past the frame. However, it is possible to inject the fluid coolant at right angles to the path of the flow of the jet, or even upstream of the jet, if a sufficiently powerful pump is used. Conduits [8 are shown welded in place but may be threaded in place if that is deemed preferable. With this arrangement, a fluid coolant, preferably but not necessarily water, is made to fiow under pressure from pump 10a, shown in Figure 2, through inlet pipe ID, T connection ll, conduits l2 and i3 and elbows l4 and I5 into headers l6 and 1?. From headers l6 and. H, the coolant enters coolant emission conduits or tubes [8 and fiows outward through orifices 19 into and within the confines of the jet blast where energy is extracted from the jet blast in the form of heat and velocity as previously discussed and pointed out. Coolant emission conduits I8 and the other conduits are protected from high temperature damage by the cooling effect of the coolant flowing through them.

An alternate type of cross tube, or transverse coolant emission conduit, designated 18a is shown in Figures 3 and 4. This is a tube which is not continuous between headers l6 and I! but extends in cantilever fashion from one of them in the manner shown, the inner or open end of tube [8a being partially flattened or streamlined in cross section as shown clearly in Figure 4 in order to reduce its resistance to the how of hot gases and thuslighten the physical load on the cantilever conduit and its supporting header. The inner or open ends of coolant emission tubes 18c. may be cut off at an angle to the path of fiOW of the jet to aid aspiration and to direct the coolant downstream. This is shown in Figure 5 where it will be seen that the open end faces diagonally downstream. Tubes I8a are of various lengths in order that coolant will be emitted at various locations within the cross sectional area of the jet blast.

In Figure '7 is another arrangement of a coolant emission frame wherein cantilever tubes l8a are utilized extending radially inward from a circular header lfia in the manner shown. Tubes l8a are again of various lengths in order that coolant will be emitted at various locations within the cross sectional area of the jet blast.

In general, therefore, the present invention comprises a framework of hollow pipes or coolant conduits suitably connected together so that fluid can be made to flow therethrough and from which the fluid is emitted within the jet blast itself. As is apparent from the foregoing descriptive matter in this specification, this emission of coolant within the confines of the jet blast itself is essential to effective operation of the device. Previous attempts to cool blasts of hot gases emanating from a reaction motor have been unsuccessful because the coolant was applied to the exterior of the blast rather than within the blast and thus very little thermal kinetic energy was transferred to the coolant with the present invention, however, the temperature and the velocity, and consequently the sound, are appreciably reduced as has been shown and pointed out in the specification.

While there have been shown and described and pointed out the fundamental novel features of this invention, as applied to a single modification, it will be. understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. A cooling andsound reducing device for the unconfined jet blast of a reaction motor comprising a series of hollow conduits of various lengths, openings in the end of said conduits for the emission of a coolant fluid at various distances from the central axis of said jet blast, means for supplying coolant fluid to said conduits and means for supporting said conduit so that said openings are within the unconfined jet blast.

2. A cooling and sound reducing device for the jet blast of a reaction motor comprising a group of conduits extending into the said jet blast, a header communicating with and supporting said conduits from without the jet blast in a cantilever manner, at least one opening in each of the said conduits for the emission of a fluid coolant at various distances from the central axis of said jet blast, means for supplying said fluid coolant to the header and conduits, means for supporting the device so that the said openings are within the confines of the jet blast, and with each coolant emission conduit having an elliptical cross section. for that portion of its length which is exposed to the jet blast, the major axis of said elliptical cross section being in thedirection; of flow of the jet blast, whereby 5 said fluid emission conduits are streamlined to the jet blast.

3. A cooling and sound reducing device for the jet blast of a reaction motor comprising a group of conduits extending into the said jet blast, a header communicating with and supporting said conduits from without the jet blast in a cantilever manner, at least one opening in each of the said conduits for the emission of a fluid coolant at various distances from the central axis of said jet blast, means for supplying said fluid coolant to the header and conduits, means for supporting the device so that the said openings are within the confines of the jet blast, and with each coolant emission conduit having that portion of its length which is exposed to the jet blast partially flattened and the major axis of its resulting cross section aligned with the flow of the jet blast, whereby said fluid emission conduits are streamlined to the jet blast.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,639,179 Hamel Aug. 16, 1927 1,791,814 Hillery Feb. 10, 1931 1,926,723 Jahnke Sept. 12, 1933 1,927,073 Ruehl Sept. 19, 1933 2,152,251 Gay Mar. 28, 1939 2,320,391 Wakefield June 1, 1943 2,359,108 Hoskins Sept. 26, 1944 2,389,059 Kurth Nov. 13, 1945 2,409,496 Kelley Oct. 15, 1946 2,546,293 Berliner Mar. 2'7, 1951 

